Question

What is the primary function of Calcitonin and Parathormone in the regulation of calcium levels?

a) Calcitonin promotes calcium release from bones, while Parathormone inhibits calcium absorption in the kidneys.

b) Calcitonin inhibits calcium absorption in the intestines, while Parathormone promotes calcium release from bones.

c) Calcitonin promotes calcium absorption in the intestines, while Parathormone inhibits calcium release from bones.

d) Calcitonin inhibits calcium release from bones, while Parathormone promotes calcium absorption in the kidneys.

Answer 1

Calcitonin reduces blood calcium levels by inhibiting bone resorption and promoting calcium excretion by the kidneys, while parathormone (PTH) increases blood calcium levels by enhancing kidney reabsorption, stimulating bone resorption, and indirectly increasing intestinal absorption.

Step-by-step explanation:

The primary functions of calcitonin and parathormone (PTH) in the regulation of calcium levels are quite opposite. Calcitonin, which is produced by the parafollicular cells of the thyroid gland, is released when calcium ion concentrations in the blood rise and functions to lower blood calcium levels. It achieves this by inhibiting osteoclast activity, which reduces the release of calcium from bones, and by stimulating the kidneys to excrete more calcium. On the other hand, parathormone is secreted by the parathyroid glands when blood calcium levels fall. It acts to raise calcium levels by enhancing reabsorption of Ca2+ by the kidneys, stimulating osteoclasts which release calcium from the bones into the bloodstream, and indirectly increasing intestinal calcium absorption through activating vitamin D synthesis.